1. Field of the Invention
The present invention relates to a plasma processing apparatus and a semiconductor device manufactured by the same apparatus. More particularly, the present invention relates to a plasma processing apparatus which is for use in manufacturing a semiconductor device by plasma discharge of reactive material gas in a sealable chamber, for example, by processing a substrate which is a material to be processed, and in which a plurality of pairs of cathode-anode bodies for performing plasma discharge are provided in the chamber so that a plurality of discharge spaces exist, and also relates to a semiconductor device manufactured by this plasma processing apparatus.
2. Description of the Related Art
A vertical type plasma processing apparatus shown in FIG. 4 is known in the conventional art as a semiconductor device manufacturing apparatus which is a kind of a general plasma processing apparatus.
The semiconductor device manufacturing apparatus shown in FIG. 4 comprises a sealable vertical type chamber 3 as a reactive vessel, and one anode 4 is substantially vertically arranged with respect to a bottom surface of the chamber 3 at its inside center portion. The anode 4 comes in contact with a heater 5. The heater 5 serves to heat a glass substrate 1 (held by a substrate holding part 12), which is a material to be processed, at a constant temperature, for example, 100° C. to 600° C. The semiconductor device manufacturing apparatus further comprises two cathodes 2, 2 which are substantially vertically arranged with respect to the bottom surface of the chamber 3 near the side wall of the inside of the chamber 3.
The semiconductor device manufacturing apparatus will be more specifically described. That is, the anode 4 and the cathodes 2, 2 are arranged so that the anode 4 is sandwiched by the cathodes 2, 2 (in a state where two pairs of the cathode-anode bodies are placed opposite) with a predetermined interval in a horizontal direction. Then, plasma discharge is performed at spaces (two spaces) between the anode 4 and each of the cathodes 2 with reactive material gas introduced from a gas introduction pipe (not shown) into the chamber 3.
The chamber 3 and the anode 4 use material such as stainless steel or aluminum alloy and use ceramics or the like for thermal insulation. Each cathode 2 is arranged so as to face the substrate 1.
In the semiconductor device manufacturing apparatus, in order that plasma discharge in each discharge space is to be the same condition by evenly supplying material gas into a plurality of (two) existing discharge spaces, it is common to provide two, the same number as that of the discharge space, power supplies 8, 8, and two matching boxes 7, 7 for matching impedance between the cathode-anode bodies and the power supplies 8, 8, and to connect each power supply 8 and matching box 7 with a power introduction wire 10.
In addition, as for a conventional plasma processing apparatus, those which improve etching or evaporation uniformity in a plasma chemical technology are known (see, for example, U.S. Pat. No. 4,264,393).
In an apparatus disclosed in U.S. Pat. No. 4,264,393, a power introduction wire which introduces electric power from a power supply is branched into a plurality of cathodes from one power supply in order to evenly distribute electric power from the power supply to the plurality of cathodes.
The aforementioned conventional plasma processing apparatuses have the following problems.
First, the apparatus shown in FIG. 4 will be described. Since this apparatus comprises a separate power supply 8 and a separate matching box 7 for each of the two discharge spaces, the cost is high.
In the case where parallel processing is performed, each processing needs to have the same condition with respect to two discharge spaces. However, since the power supplies 8, 8 have variation, the input power is not necessarily truly the same even when power values are set to be the same. Therefore, since this apparatus is required to perform adjustment according to the respective discharge spaces, control for individual discharge is very complicated, and there is a problem in that variation occurs readily at each discharge.
Next, the apparatus disclosed in U.S. Pat. No. 4,264,393 will be described. In this apparatus, the number of the power introduction wires from the power supply to the cathode is set to be ½ of that of the discharge spaces. It is assumed herein that a homogeneous film is produced between the surfaces of the cathode and the anode by plasma discharge.
However, actually, it is well known that a cathode film obtained by the plasma processing apparatus is inferior in quality compared to an anode film.
In the case where electric power is supplied to each cathode with a power introduction wire branched from one power supply, not only a branching filter is required at every branched point in order to evenly distribute electric power by such a branch method, but also the power introduction wire from the power supply to each cathode differs largely in length.
Consequently, even if a power coaxial cable whose impedance is constant is used, considerable variation can be expected in electric power to be supplied to each cathode. As a result, the apparatus in which parallel processing is assumed to be performed has very large variation in every branch.